linux-kernel - Re: [PATCH v4 05/10] powerpc/dt_cpu

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Date:   Fri, 17 Jul 2020 15:44:13 +1000
From:   Jordan Niethe <jniethe5@...il.com>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>, mikey@...ling.org,
        apopple@...ux.ibm.com, Paul Mackerras <paulus@...ba.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        naveen.n.rao@...ux.vnet.ibm.com, peterz@...radead.org,
        jolsa@...nel.org, oleg@...hat.com, fweisbec@...il.com,
        mingo@...nel.org, pedromfc@...ibm.com, miltonm@...ibm.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 05/10] powerpc/dt_cpu_ftrs: Add feature for 2nd DAWR

On Fri, Jul 17, 2020 at 2:10 PM Ravi Bangoria
<ravi.bangoria@...ux.ibm.com> wrote:
>
> Add new device-tree feature for 2nd DAWR. If this feature is present,
> 2nd DAWR is supported, otherwise not.
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
> ---
>  arch/powerpc/include/asm/cputable.h | 7 +++++--
>  arch/powerpc/kernel/dt_cpu_ftrs.c   | 7 +++++++
>  2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
> index e506d429b1af..3445c86e1f6f 100644
> --- a/arch/powerpc/include/asm/cputable.h
> +++ b/arch/powerpc/include/asm/cputable.h
> @@ -214,6 +214,7 @@ static inline void cpu_feature_keys_init(void) { }
>  #define CPU_FTR_P9_TLBIE_ERAT_BUG      LONG_ASM_CONST(0x0001000000000000)
>  #define CPU_FTR_P9_RADIX_PREFETCH_BUG  LONG_ASM_CONST(0x0002000000000000)
>  #define CPU_FTR_ARCH_31                        LONG_ASM_CONST(0x0004000000000000)
> +#define CPU_FTR_DAWR1                  LONG_ASM_CONST(0x0008000000000000)
>
>  #ifndef __ASSEMBLY__
>
> @@ -497,14 +498,16 @@ static inline void cpu_feature_keys_init(void) { }
>  #define CPU_FTRS_POSSIBLE      \
>             (CPU_FTRS_POWER7 | CPU_FTRS_POWER8E | CPU_FTRS_POWER8 | \
>              CPU_FTR_ALTIVEC_COMP | CPU_FTR_VSX_COMP | CPU_FTRS_POWER9 | \
> -            CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10)
> +            CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10 | \
> +            CPU_FTR_DAWR1)
>  #else
>  #define CPU_FTRS_POSSIBLE      \
>             (CPU_FTRS_PPC970 | CPU_FTRS_POWER5 | \
>              CPU_FTRS_POWER6 | CPU_FTRS_POWER7 | CPU_FTRS_POWER8E | \
>              CPU_FTRS_POWER8 | CPU_FTRS_CELL | CPU_FTRS_PA6T | \
>              CPU_FTR_VSX_COMP | CPU_FTR_ALTIVEC_COMP | CPU_FTRS_POWER9 | \
> -            CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10)
> +            CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10 | \
> +            CPU_FTR_DAWR1)
Instead of putting CPU_FTR_DAWR1 into CPU_FTRS_POSSIBLE should it go
into CPU_FTRS_POWER10?
Then it will be picked up by CPU_FTRS_POSSIBLE.
>  #endif /* CONFIG_CPU_LITTLE_ENDIAN */
>  #endif
>  #else
> diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
> index ac650c233cd9..c78cd3596ec4 100644
> --- a/arch/powerpc/kernel/dt_cpu_ftrs.c
> +++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
> @@ -574,6 +574,12 @@ static int __init feat_enable_mma(struct dt_cpu_feature *f)
>         return 1;
>  }
>
> +static int __init feat_enable_debug_facilities_v31(struct dt_cpu_feature *f)
> +{
> +       cur_cpu_spec->cpu_features |= CPU_FTR_DAWR1;
> +       return 1;
> +}
> +
>  struct dt_cpu_feature_match {
>         const char *name;
>         int (*enable)(struct dt_cpu_feature *f);
> @@ -649,6 +655,7 @@ static struct dt_cpu_feature_match __initdata
>         {"wait-v3", feat_enable, 0},
>         {"prefix-instructions", feat_enable, 0},
>         {"matrix-multiply-assist", feat_enable_mma, 0},
> +       {"debug-facilities-v31", feat_enable_debug_facilities_v31, 0},
Since all feat_enable_debug_facilities_v31() does is set
CPU_FTR_DAWR1, if you just have:
{"debug-facilities-v31", feat_enable, CPU_FTR_DAWR1},
I think cpufeatures_process_feature() should set it in for you at this point:
            if (m->enable(f)) {
                cur_cpu_spec->cpu_features |= m->cpu_ftr_bit_mask;
                break;
            }

>  };
>
>  static bool __initdata using_dt_cpu_ftrs;
> --
> 2.26.2
>